Bone anchors for attaching suture, bone and/or soft tissue to bone are well known in the art. See, for example, U.S. Pat. Nos. 4,898,156; 5,046,513; 5,192,303; 4,899,743; 4,968,315; 4,946,468; 5,002,550; 5,207,679; and 5,217,486; and U.S. patent applications Ser. Nos. 07/981,011; 08/075,168; 08/030,657; 08/197,927; 08/098,599; and 08/180,425.
Installation tools for deploying such bone anchors in bone are also well known in the art. See, for example, the foregoing U.S. patents and patent applications.
Complete details of the construction and operation of the foregoing exemplary bone anchors and bone anchor installation tools are provided in the above-identified patents and patent applications, which patents and patent applications are hereby incorporated herein by reference.
While the bone anchors disclosed in the foregoing U.S. patents and patent applications have proven more than satisfactory for most applications, it has been noted that certain problems can occur when using these bone anchors in special situations.
More particularly, with some of the foregoing bone anchors (e.g. the anchors disclosed in U.S. Pat. Nos. 5,207,679 and 5,217,486), it can be very difficult to form the bone anchors in a very, very small size, e.g. bone anchors having a length on the order of 3.7 millimeters or so. This is because the maximum radius of curvature which can be imparted to the anchor's barbs is limited by the characteristics of the material out of which the barbs are formed. When using pseudoelastic materials of the sort preferred for forming the barbs, this consideration can become significant as the size of the anchor is reduced to the point where the anchor has a length on the order of 3.7 millimeters or so. In particular, as one progressively reduces the size of the barb after the maximum radius of curvature has been encountered, the overall length of the barb must necessarily decrease. Accordingly, less barb material is available for secure attachment to the anchor body and/or less barb material is available for engaging the surrounding bone during anchor deployment.
Furthermore, while the bone anchor installation tools disclosed in the foregoing U.S. patents and patent applications have proven more than satisfactory for most applications, it has been noted that certain problems can occur when using these installation tools in special situations.
More particularly, with some of the foregoing installation tools (e.g. the installation tools disclosed in U.S. Pat. Nos. 4,898,156; 5,046,513; 5,192,303; and 4,899,743), the portion of the tool which carries the anchor (i) is wider than the body of the anchor itself, and (ii) must be positioned within the bone during anchor deployment. As a result of this construction, the bone hole must be formed significantly larger than the body of the anchor in order to permit anchor deployment. This can be a disadvantage in certain situations where it may be necessary to form the smallest possible hole in the bone.
With others of the foregoing installation tools (e.g. the installation tools disclosed in U.S. Pat. No. 5,217,486 and U.S. patent application Ser. No. 08/098,599), the portion of the tool which carries the anchor does not need to be received by the bone during anchor deployment. Instead, only a relatively thin drive pin enters the bone during anchor deployment. The drive pin is formed so that it has a diameter less than the diameter of the anchor body. As a result of this construction, the bone hole can be formed so that it has substantially the same width as the anchor body. However, it has also been found that where the installation tool is being used to set extremely small bone anchors, the drive pin must be so thin that it may bend or otherwise deform in certain circumstances. When this occurs, it may affect anchor deployment and/or render the installation tool unusable for subsequent anchor deployments.
In addition to the foregoing, it has also been found that where the installation tools are being used in conjunction with anchors adapted to attach suture to bone, it can be very helpful to provide suture management means for controlling the disposition of the one or more free suture ends. In this respect it is noted that with some of the foregoing installation tools (e.g. the installation tools disclosed in U.S. Pat. Nos. 4,946,468 and 5,002,550), such suture management means are provided. While such suture management means work well enough for most applications, it has been found that alternative suture management means could be helpful in some situations.
Furthermore, as the overall size of a bone anchor is decreased, it becomes less and less practical for the bone anchor to be mounted to the installation tool in the field (e.g. the operating room). Instead, it becomes necessary to mount the bone anchor in the installation tool at the point of manufacture. However, with the bone anchor installation tools of the type disclosed above, this means that the installation tool cannot easily be reused to deploy a subsequent anchor. Thus, with bone anchor installation tools of the sort disclosed above, the installation tool must generally be made so as to be disposable when it is to be used with a very, very small anchor. This can be undesirable in many circumstances.
Additionally, as the overall size of the bone anchor is decreased, it becomes more important to provide additional means for ensuring that the bone anchor does not become separated from the installation tool prior to deployment of the bone anchor in bone.